The Near Infrared Spectrograph (NIRSpec) is one of four science instruments aboard the James Webb Space
Telescope (JWST) scheduled for launch in 2018. NIRSpec is sensitive in the wavelength range from ~0.6 to 5.0
micron and will be capable of obtaining spectra from more than a 100 objects simultaneously by means of a
programmable micro shutter array. It will also provide an integral eld unit for 3D spectroscopy and xed slits
for high contrast spectroscopy of individual sources and planet transit observations. We present results obtained
during the rst cryogenic instrument testing in early 2011, demonstrating the excellent optical performance of
the instrument. We also describe the planning of NIRSpecs forthcoming second calibration campaign scheduled
for early 2013.

Stephan M. Birkmann, European Space Research and Technology Ctr. (Netherlands)Pierre Ferruit, European Space Research and Technology Ctr. (Netherlands)Torsten Böker, European Space Research and Technology Ctr. (Netherlands)Guido De Marchi, European Space Research and Technology Ctr. (Netherlands)Giovanna Giardino, European Space Research and Technology Ctr. (Netherlands)Marco Sirianni, European Space Research and Technology Ctr. (Netherlands)Martin Stuhlinger, European Space Astronomy Ctr. (Spain)